ProjectSummary/Abstract Drug addiction is a chronic, relapsing disorder in which drug-related associations are capable of exerting tremendouscontroloverbehaviorlongafterdrugconsumptionhasceased.Drugsofabusecauselong-lasting functionalandstructuralalterationsinthebrain?srewardcircuits,suchasthenucleusaccumbens.Recentwork hasproposedthatepigeneticmodifications,suchashistonemodificationorDNAmethylation,areresponsible forthiscocaine-inducedplasticity.Moreover,novelfindingsrevealthatdrugsofabuse,suchascocaine,induce epigeneticchangesinthenucleusaccumbensandthatthesechangescontrolcocaine-relatedneuroadaptations. However, very little is known about how single, gene specific epigenetic modifications at genes implicated in addiction affect the reward circuit. This proposal will examine the effect of specific modifications of DNA methylationontherewardcircuitbothinvitroandinvivo.Thespecificaimsofthisproposedresearcharethat: 1)identifygeneexpressionandDNAmethylationchangesinNAcinresponsetodopaminegenome-wide,2) examine the role of gene-specific epigenetic modification on the NAc, and 3) characterize the role of gene- specific epigenetic modification on behavior. This will be achieved using a catalytically deactivated CRISPR- Cas9 fusion protein system, which will be used to alter gene-specific epigenetic states recruitment of a DNA methyltransferaseenzyme.Thiscontributionissignificantbecauseitisthefirststepinidentifyingthespecific epigeneticchangesthatarecriticalfortheneuralandbehavioralchangesfollowingexposuretodrugsofabuse. Theoverallhypothesisisthatsite-specificepigeneticmodificationsarecriticalcomponentsofbiochemicaland behavioralresponsestodrugsofabuse.Thepersistingalterationsthatoccurafterexposuretodrugsofabuse are believed to drive pathological drug seeking and relapse long after drug use has ceased. Therefore, understandingthesechangeswilladvancethefieldclosertotargetedtherapeuticsthatareabletoreversethe alterations.